1. Field of the Invention
This invention relates to a color image communication apparatus.
2. Related Background Art
Heretofore, in order to obtain a plurality of copies of an original with a color facsimile machine, it is necessary to either scan the original the same number of times, or store the data in a memory.
In addition, the color facsimile requires standardization of the data which it processes. This means that RGB data of the scanner must be converted to NTSC standard RGB data, leading to deterioration of the image quality. This is often undesirable, especially when the facsimile is in the copy mode, where high image quality is required for the copy to be a faithful reproduction of the original.
Further, in the scanning part of a color facsimile apparatus, a main scanning line of an original image is read out by an elongate line sensor through electric scanning, and the line sensor is mechanically fed in the auxiliary scanning direction to repeat one-line reading, thereby reading the entire original image. This conventional method is called a raster scan reading system.
However, due to limitations in semiconductor manufacture, it is frequently difficult and sometimes impossible to manufacture an elongate line sensor which can read a large size original image (such as an A4 or A3 size original). The conventional method of producing such a line sensor is by connecting a plurality of short line sensors. This method, however, poses problems in the accuracy of alignment for connection. Because it is impossible to set a plurality of line sensors along a straight line, in practice line sensors are staggered with respect to one another for several pixels in the auxiliary scanning direction. In this case, however, an extremely large load is inevitable for electrically correcting the deviation in the auxiliary scanning direction. Therefore, even in magnified image reading, the sensors in a staggered arrangement cannot read the same line unless such measure is provided as varying the read timing according to the auxiliary direction scan speed.
Further, in the prior art, an image is focused on a line sensor not by using close-contact-to-original type sensors, but rather by using a scale-reducing optical system.
Further, in a line sensor requiring a scale-reducing optical system, an element corresponding to one pixel is extremely small in size, and it is difficult to apply filters for color sensors.
Further, if the resolution when reading an original image is increased with respect to all the above prior art examples, the difficulty of implementation and the difficulty of filter application are increased.
Further, the prior art apparatus usually adopts the raster scan for reading, transmitting and printing an image. Such processing, however, frequently requires a buffer as long as one line in the raster direction.
Accordingly, it is thought to adopt a shuttle scan system for reading an image. With a shuttle scan system, the size of the line buffer necessary for individual image processings in the raster direction is reduced. For example, when scanning an A4 size original with a 400 dot per inch (dpi) resolution, the buffer size may be reduced from 3,456 pixels to 128 pixels, thus permitting a reduction in the size of the required memory. In a facsimile apparatus or the like, however, raster data are dealt with in image communication with the destination partner. This means that the scanner or printer requires a vertical/horizontal conversion section between shuttle scan and raster scan.